Fig. 4. IRE1α activation promotes SCD1/2-mediated lipid accumulation during B cell activation and plasma cell differentiation.

(A-B) In vivo intracellular lipid content in B cell populations of splenocytes from Ire1α^fl/fl MRL.Fas^lpr mice (n=6). (A) Representative FACS analysis of lipid staining for B cells from the indicated populations. (B) Lipid quantification expressed of Bodipy 493/503 staining. (C-F) In vitro intracellular lipid content in B cell populations of splenocytes from Ire1α^fl/fl MRL.Fas^lpr mice. Primary naïve B cells were isolated from splenocytes, and stimulated with LPS (1mg/ml) or anti-CD40 (4μg/ml) for 2 and 3 days, respectively (n=4). (G - J) RT-qPCR detection of expression levels of Scd1 (G), Scd2 (H), Ire1α (I), and Xbp-1s (J) in naïve B cells, activated B cells, and plasma cells (n=3). (K - N) Primary B cells were isolated from 4 to 5-week old of Cd19- Ire1α^Δ mice and their littermate control mice and stimulated with LPS (K & L) or anti-CD40 (M & N) in vitro for 4 days (n=4). Representative FACS analysis (K & M) and data plots (L & N) of lipid staining for B cells from indicated sources. (O) Representative FACS analysis of cell size of activated B cell and plasma cells from Cd19- Ire1α^Δ mice and their littermate controls. Significance determined by an unpaired Student’s t –test (two-tailed). * p<0.05, ** p<0.01, *** p<0.001, and **** p<0.0001.